This invention is directed generally to non-chloride containing regenerant compositions of potassium acetate, at least one surfactant and at least one chelating agent as well as methods for efficient regeneration of water softeners utilizing the regenerant compositions are disclosed. A preferred regenerant composition is a solution of potassium acetate, citric acid and octyl phenol ethoxylate.
Hard water contains certain minerals, such as calcium and magnesium, which can be detrimental to a water system. In particular, these minerals will form an undesirable precipitate when they come in contact with soap, and will scale in piping, water heaters, pots, and washing machines. To alleviate this problem, water softening systems have become quite popular. Such systems convert hard water to soft water by removing minerals (mainly magnesium and calcium) from the hard water. This is done by a process known as cation exchange. In this process, sodium or other cations are substituted for calcium and magnesium ions in the hard water.
The process basically involves running hard water through an exchange media, such as an organic resin bed or zeolite softener regenerated with exchangeable cations, such as sodium ions or potassium ions. These ions are attached to the beads due to an inherent negative charge in the beads. A brine, consisting of sodium chloride or potassium chloride dissolved in water, is run over the beads for regeneration. Once the beads are regenerated, the system is ready to operate by running hard water through the beads. Cation exchange thus takes place, and the resultant effluent water is soft.
Eventually, the sodium or potassium ions carried by the beads will be depleted, or virtually depleted. The beads will then need to be regenerated with sodium or potassium. The regeneration process is the same as the initial charging process in that brine passes over the beads. However, during regeneration, any effluent brine will contain magnesium, calcium, and sodium chloride or potassium chloride, as is well known in the art.
The effluent liquid from the regeneration process will have a relatively high concentration of NaCl and KCl as high as 5-10%. Other elements, such as manganese, iron, sodium, magnesium, and potassium, either naturally existing in the water or collected as a result of water softening, contribute to the TDS of the effluent waste water, as well as the alkali chlorides.
The high TDS effluent is then sent through a drain to the sewer system as any drain water from a house. Due to recent environmental concerns and the desire for water reclamation, many municipalities are enacting or considering ordinances limiting the amount of chlorides and/or TDS that can be sent through sewer systems. These limits often are on the order of 250 ppm chlorides and 500 ppm TDS. Since effluent in the regeneration process far exceeds these maximum acceptable amounts, water softeners have been banned by some municipalities.
To meet the new stricter requirements, the residential softener can be regularly changed out to remove the undesirable products without flushing them into the sewer system. Such change outs typically involve service personnel periodically traveling to the houses or offices having water softeners, removing the tanks with the exhausted beads. The tanks of beads are taken to a facility for a centralized regeneration process. Once regenerated, these tanks of beads can again be used to replace tanks with exhausted beads.
Therefore, there is a need for an alternative method which allows efficient regeneration without release of chloride by-products to a sewer system.
It is an object of this invention to provide a composition and a method for regenerating water softeners without releasing chlorides.
It is a further object of this invention to provide an efficient method which allows accurate metering of the necessary amount of regenerating solution for most efficient regeneration of water softeners.
The invention is directed to a non-chloride containing regenerant composition for regenerating a strong acid cation exchange resin consisting essentially of:
from about 5 to about 60 weight percent of at least one of potassium salt selected from the group consisting of potassium acetate and potassium formate;
from about 0.0005 to about 0.1 weight percent of at least one surfactant;
from about 0.01 to about 1 weight percent of at least one chelating or sequestering agent; and
the balance water.
The invention is also directed to a method for regenerating a spent strong acid cation exchange resin without release of chloride comprising the step of contacting said resin with a regenerating amount of a solution of
from about 5 to about 60 weight percent of at least one potassium salt selected from the group consisting of potassium acetate and potassium formate;
from about 0.0005 to about 0.1 weight percent of at least one surfactant;
from about 0.01 to about 1 weight percent of at least one chelating or sequestering agent;
and the balance water.
The invention is also directed to a method for treating a spent strong acid cation exchange resin to regenerate said resin comprising the steps of:
diluting a concentrated solution of at least one potassium salt selected from the group consisting of potassium acetate and potassium formate, at least one surfactant and at least one chelating or sequestering agent to form a dilute solution of from about 5 to about 60 weight percent potassium acetate; from about 0.0005 to about 0.1 weight percent of at least one surfactant; from about 0.01 to about 1 weight percent of at least one chelating agent; and the balance water; and then
passing said solution through a bed said resin.
For the practice of any aspect of this invention, the potassium salt may be potassium acetate and the amount of potassium acetate may be from about 10 to about 25 weight percent, and more preferably from about 10 to about 15 weight percent. A presently preferred surfactant is octyl phenol ethoxylate and a presently preferred chelating or sequestering agent is citric acid.